Electric submersible pump with reduced vibration

Abstract

An electric submersible pump (ESP) with reduced vibration is provided. In an implementation, an ESP section has radial bearings placed at shaft locations of reduced vibration to reduce wear. The locations of reduced vibration are selected to avoid areas of high vibration and vibrational waves that reinforce each other due to structure resonance and natural excitation frequencies. In an implementation, a radial bearing is positioned at a node of reduced vibration of a standing vibrational wave. In an implementation, a succession of multiple radial bearings are spaced at different intervals from each other to avoid conventional even spacing of the bearings that causes standing waves, resonance waves, and vibrational waves at natural excitation frequencies. In an implementation, a span between adjacent radial bearings is selected to spare other adjacent bearings at different spans the effects of vibrations that may extend over a range of excitation frequencies in the ESP section.

The invention claimed is: 
     
       1. An electric submersible pump (ESP), comprising:
 an ESP section; 
 a shaft for rotation in the ESP section; and 
 a plurality of bearings spaced along the shaft and configured to provide radial support of the shaft, wherein the plurality of bearings are spaced at different bearing spans from each other along the shaft, wherein a length of each bearing span is unique, and wherein the length of each successive bearing span along the shaft is at least 5 percent different from the length of each neighboring bearing span. 
 
     
     
       2. The ESP of  claim 1 , comprising at least four successive bearings along the shaft. 
     
     
       3. The ESP of  claim 1 , wherein the ESP section is selected from the group consisting of a pump, a motor, and a protector.